Functional Overview

This chapter provides the overview of the features offered by the SHFLI Lock-in Amplifier. The first section contains the description of the functional diagram, and the hardware and software feature list. The following section details the front panel and the back panel of the measurement instrument. The last section provides product selection and ordering support.

Features

The SHFLI Lock-in Amplifier consists of several internal units that process digital data (light blue color) and several interface units processing analog signals (dark blue color). The front panel is depicted on the left-hand side and the back panel is depicted on the right-hand side. The arrows between the panels and the interface units indicate selected physical connections and the data flow.

The orange blocks are optional units that can be either ordered at purchase or upgraded later. The SHFLI Lock-in Amplifier has 2 physical channels each with its own signal input and output, auxiliary input and digital inputs and outputs. The ordering guide details the currently available upgrade options.

Figure 1: SHFLI instrument functional diagram

The signal to be measured is usually connected to one of the two SHFLI signal inputs where it is amplified to a defined range and mixed down to an intermediate frequency (IF) through a double-superheterodyne scheme and digitized at very high speed if above 800 MHz, or directly digitized if below this frequency threshold. The resulting samples are fed into the digital signal processor that contains 8 dual-phase demodulators. The results of the demodulation are fed into a digital interface to be transferred to the host computer through the LAN or USB interface, and can also be routed to the auxiliary outputs on the front panel of the SHFLI. Two low-distortion signal outputs provide the signal generator functionality.

The numerical oscillators generate sine and cosine pairs that are used for the demodulation of the input signal and also for the generation of the SHFLI output signals. For this purpose, when the SHFLI-MF Multi-Frequency option is present, the Output Adder can generate a linear combination of the oscillator outputs to generate a multi-frequency output signal. After the digital-to-analog conversion, the output signal is either routed directly to the output connectors, if its final frequency is below 800 MHz, or through the double-superheterodyne upconversion path if its final frequency needs to be above this frequency.

Hardware trigger and reference signals are used for various purposes inside the instrument, such as triggering demodulation and oscilloscope data acquisition, to acquire or generate an external reference signal, or triggering other equipment.

Lock-in Operating Modes

• Internal reference mode
• External reference mode (coming later in 2023)
• Dual-lock-in operation (two independent lock-in amplifiers in the same box)
• Triple-harmonic mode (simultaneous measurement at three frequencies within the measurement window that are harmonic of the Numerical Oscillator frequency)
• Arbitrary frequency mode (with SHFLI-MF option, simultaneous measurement at up to eight arbitrary frequencies within the measurement window)

Super-high-frequency Signal Inputs

• 2 low-noise SHF Inputs, DC - 8.5 GHz frequency range, 1 GHz bandwidth
• Variable input range, selectable from 1 mV to 1 V peak (10 mV to 1 V in Baseband)
• Selectable AC/DC coupling in Baseband

Super-high-frequency Signal Outputs

• Low-noise SHF Outputs, DC - 8.5 GHz frequency range, 1 GHz bandwidth
• Variable output range, selectable from 10 mV to 1 V peak (10 mV to 0.5 V in Baseband)

Demodulators & Reference

• Up to 8 dual-phase demodulators
• Up to 8 programmable numerical oscillators
• Up to 2 external reference signals (coming later in 2023)
• Up to 4 input and up to 4 output trigger signals
• Individually programmable demodulator filters
• 128-bit internal processing
• 64-bit resolution demodulator sample
• 48-bit internal reference resolution

Auxiliary Input and Outputs

• 4 high-speed auxiliary outputs for user-defined signals, 25 MHz bandwidth, 14 bit
• 4 high-precision auxiliary outputs for user-defined signals, 200 kHz bandwidth, 18 bit
• 2 auxiliary inputs, general purpose

High-speed Connectivity

• SMA connectors on front and back panel for triggers, signals and external clock
• USB 3.0 high-speed host interface
• LAN/Ethernet 1 Gbit/s controller interface
• DIO: 32-bit digital input-output port
• Clock input/output connectors (10/100 MHz)

Extensive Time and Frequency Domain Analysis Tools

• Numeric tool
• Plotter
• Oscilloscope
• Sweeper and Frequency response analyzer
• FFT spectrum analyzer

Software Features

• Web-based, high-speed LabOne® user interface with multi-instrument control
• Data server with multi-client support
• API for Python and MATLAB®

Front Panel Tour

The front panel SMA and BNC connectors and control LEDs are arranged as shown in Figure 2 and listed in Table 1.

Figure 2: SHFLI Lock-in Amplifier front panel

Table 1: SHFLI Lock-in Amplifier front panel description

Position	Label / Name	Description
A	Aux In	analog Auxiliary Input, max. 10 V
B	Signal Output	single-ended analog Signal Output, DC-8.5 GHz, max. 1 V peak
C	Trig Out	TTL Trigger Outputs 1 to 4
D	Trig In	TTL Trigger Inputs 1 to 4
E	Signal Input	single-ended analog Signal Input, DC-8.5 GHz, max. 1 V peak
F	High Precision	high-precision auxiliary outputs 1 to 4
G	High Speed	high-speed auxiliary outputs 1 to 4
H	multicolor LEDs	off Instrument off or uninitialized blink all LEDs blink for 5 seconds → indicator used by the Identify Device functionality
		Busy	unused
		Ext. Clock	off 10/100 MHz External Clock Signal not present/detected blue 10/100 MHz External Clock Signal is present and locked on to yellow 10/100 MHz External Clock Signal present, but not locked on to red 10/100 MHz External Clock Signal present, but lock failed
		ZSync	unused
		Status	off Instrument off or uninitialized blue Instrument is initialized and has no warnings or errors yellow Instrument has warnings red Instrument has errors
J	Soft power button	Power button with incorporated status LED off Instrument off and disconnected from mains power blue flashing rapidly (>1/sec): Firmware is starting flashing slowly (<1/sec): Firmware ready, waiting for connection constant: Instrument ready and active connection over USB or Ethernet red breathing: Instrument off but connected to mains power → safe to power off using the rear panel switch, or restart using the soft power button flashing: Instrument booting up constant: Fatal error occurred

Back Panel Tour

The back panel is the main interface for power, control, service and connectivity to other ZI instruments. Please refer to Figure 3 and Table 2 for the detailed description of the items.

Figure 3: SHFLI Lock-in Amplifier back panel

Table 2: SHFLI Lock-in Amplifier back panel description

Position	Label / Name	Description
A	Earth ground	4 mm banana jack connector for earth ground, electrically connected to the chassis and the earth pin of the power inlet
B	AC 100 - 240 V	Power inlet, fuse holder, and power switch
C	MDS 1	SMA: bidirectional TTL ports for multi-device synchronization
D	MDS 2	SMA: bidirectional TTL ports for multi-device synchronization
E	USB 1	Maintenance USB port. Only for instrument maintenance, not regular operation. Please use USB 2 port (see position H) instead.
F	LAN 1GbE	1 Gbit LAN connector for instrument control and data acquisition
G	DIO 32bit	32-bit digital input/output (DIO) connector
H	USB 2	Universal Serial Bus (USB) 3.0 port for instrument control and data acquisition
I	ZSync Secondary	unused Attention: This is not an Ethernet plug, connection to an Ethernet network might damage the instrument
J	ZSync Primary	unused Attention: This is not an Ethernet plug, connection to an Ethernet network might damage the instrument
K	External Clk In	external clock Input (10 MHz/100 MHz) for synchronization with other instruments
L	External Clk Out	external clock Output (10 MHz/100 MHz) for synchronization with other instruments

Ordering Guide

Table 3 provides an overview of the available SHFLI products. Upgradeable features are options that can be purchased anytime without the need to send the Instrument back to Zurich Instruments.

Table 3: SHFLI Instrument product codes for ordering

Product code	Product name	Description	Field upgrade possible
SHFLI	SHFLI Lock-in Amplifier	base lock-in amplifier	-
SHFLI-MF	SHFLI-MF Multi-frequency	option	yes
SHFLI-MOD	SHFLI-MOD AM/FM Modulation	option	yes1
SHFLI-PID	SHFLI-PID Quad PID/PLL Controller	option	yes

¹ Requires SHFLI-MF Multi-frequency option

Table 4: Product selector SHFLI

Feature	SHFLI	SHFLI + SHFLI-MF	SHFLI + SHFLI-PID	SHFLI + SHFLI-MF + SHFLI-PID
Internal reference mode	yes	yes	yes	yes
External reference mode	yes	yes	yes	yes
Dual-channel operation (2 independent measurement units)	yes	yes	yes	yes
Signal generators	2	2	2	2
Superposed output sinusoidals per generator	1	up to 8	1	up to 8
Triple-harmonic mode	yes	yes	yes	yes
Multi-frequency mode	-	yes	-	yes
Arbitrary frequency mode	-	yes	-	yes
Number of demodulators	8	8	8	8
Simultaneous frequencies	2	8	2	8
Simultaneous numerical oscillator harmonics	4+4	-	4+4	-
External references	2	2	2	2
PID controllers	-	-	4	4
Dynamic reserve	100 dB	100 dB	100 dB	100 dB
Lock-in range	8.5 GHz	8.5 GHz	8.5 GHz	8.5 GHz
USB 3.0	yes	yes	yes	yes
LAN 1 Gbit/s	yes	yes	yes	yes